CODEWITHSUNDEEP
javaalgorithmsearchbinarybinary-search
shahul ha
shahul ha

Reputation: 123

Binary Search Program returning wrong position

I wrote a recursion program for binary search as you see I am trying to find the position of the target =21 in the given array which sohould return me position as 2. However my output is 1. While I debug the it matches att arr[start]=target, However it straight was jumps to the line findTheNumber(arr, mid + 1, end, target); then next line and then return mid.. Just wondering why my return is breaking off at the "return start"

 package Recursion;

 public class BinarySearch {
 static int  mid = 0;

 public static int findTheNumber(int[] arr, int start, int end, int target) {


    if (arr[start] == target) {
        return start;
    }

    mid = (start + end) / 2;

    if (arr[mid] == target) {
        return mid;
    } 

    if (target >arr[mid]) {
            findTheNumber(arr, mid + 1, end, target);
        } else if (target <arr[mid]) {
            findTheNumber(arr, start, mid-1, target);
        }
        return mid;
    }



public static void main(String[] args) {
    int[] arr = { 10, 12,21 };
    int start = 0;
    int end = arr.length - 1;

    int target = 21;

    System.out.println(findTheNumber(arr, start, end, target));

}

}

Upvotes: 1

Views: 152

Answers (1)

WolverinDEV
WolverinDEV

Reputation: 1524

if (target >arr[mid]) {
    findTheNumber(arr, mid + 1, end, target);
} else if (target <arr[mid]) {
    findTheNumber(arr, start, mid-1, target);
}

You're just returning your mid point there, not the actual result of the recursive call.
Your code should look like: 

if (target >arr[mid]) {
    return findTheNumber(arr, mid + 1, end, target);
} else if (target <arr[mid]) {
    return findTheNumber(arr, start, mid-1, target);
}

Upvotes: 5

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